1. Field of the Invention
The present invention relates to broadcast printing for enabling a user to simultaneously send documents or messages to several destinations and printing the documents or messages through an intranet or the internet at work or school. More particularly, the present invention relates to a method and apparatus for broadcast printing via a network, by which data to be printed is simultaneously transmitted to a plurality of destinations and printed, using an explicit multicast (Xcast) method.
2. Description of the Related Art
In order to simultaneously send data for printing to several destinations and printing the data among devices connected through a network (hereinafter, this indicates broadcast printing), a specific network environment including a server, a router, and a client (e.g., a network printer) is required. The server is a device for controlling connections between computers and other electronic devices in a network or is a personal computer for transmitting data to the router for printing.
The router is a device for connecting separate networks using the same transmission protocol and determining a network route according to a routing table. The router transmits the data received from the server to the client by selecting the most efficient route among several routes. The client interprets the data received from the router, converts it into an image for printing, and then prints the image.
In order to transmit data for printing from the server to a plurality of clients via a network, unicast, broadcast, and multicast methods are used. When the unicast method is used, the server sets up connections to all clients and repetitively transmits data for printing to the respective clients as many times as the number of clients. For instance, if there are 10 clients, the server sets up 10 connections and transmits the data to the respective clients 10 times. Thus, the load on the server and the network is very high.
When the broadcast method is used, the server transmits data for printing once and all clients in the network receive the same data. In this case, the data is also transmitted to clients which do not want to receive the data, and thus, these clients are unnecessarily burdened with receiving unwanted data.
In order to solve this problem, the multicast method is suggested. In the multicast method, the server is able to transmit data for printing only to clients which want to receive the data in the network by using an Internet group management protocol (IGMP). The IGMP is an Internet protocol which allows a computer connected the internet to report its multicast group membership to a nearby router. The multicast method operates based on group addresses and an address area of class D is designated in an Internet protocol (IP) address for the group addresses. When transmitting data, one of the addresses in the class D is set up as a destination address of an IP header.
In order to understand the multicast method, it is assumed that broadcast printing with respect to a group A is performed. First, operations of the server to transmit data for printing will be explained. The server transmits the data to the group A via the router by inserting addresses of the group A into a destination address field of the IP header. Clients, which belong to the group A, register for the group A in advance so as to receive the data and thus the clients send registration messages of the IGMP to the router. The registration message is managed by the router in the network. When the router receives the data which is transmitted from the server to destinations of the group A, it sends the data to destinations, or respective clients, based on information of the group which it manages, and the clients interpret and print the received data.
The multicast method is one of the most efficient methods among the aforementioned methods for transmitting data to a plurality of clients and performing broadcast printing. In this method, the IGMP is used to manage clients who want to print the data. When the clients send the registration messages of the IGMP for broadcast printing to the router, the router receives the registration messages and forms a transmitting tree for data transmitting. In this case, the router performs many operations and the load on the router is high. Therefore, the broadcast printing cannot be done quickly.